1. Field of the Invention
This invention relates to a quantum effective device comprising quantum well boxes, and more specifically, to a quantum effective device comprising quantum well boxes having a microstructure which is useful as a functional material utilizing a quantum size effect.
2. Description of the Prior Art
In recent years, it has been higly expected to develop a new functional material utilizing a quantum size effect. One example of application of such a functional material is a quantum well laser for emitting monochromonized light. The prior level of the technique of forming a microstructure has been unable to realize such expectation.
One of the techniques of producing a new functional material is the technique of quantum well boxes. To realize the quantum well effect in, for example, a GaAs system the size of quantum well boxes must be on the order of 100 .ANG. for realizing the quantum well effect. The method now available to form quantum well boxes is fine working by electron beam lithography (see H. Termkin, G. J. Gossard, M. B. Panish and N. G. Chu. Appl. Phys. Lett., 50 48 (1987)). However, it is extremely difficult to perform fine working of the order of 100 .ANG., and it is said that the limit of fine working by electron beam lithography is about 300 .ANG.. In addition, a serious problem exists with the electron beam lithography in that fine controllability for size distribution of the quantum well boxes is lacking, and that owing to reactive ion etching during fine working, the occurrence of damages cannot be avoided in the crystals in the quantum well boxes existing in the interface between the quantum well boxes and the substrate. If the size of the quantum well boxes are not uniform in size, the quantum well effect will not be produced effectively. Furthermore, if damages should be done to the crystals of the quantum well boxes, some defects would be generated in the quantum well boxes, resulting in the electron trapping at the interfaces between the quantum well boxes and surrounding clad crystals.
Accordingly to form quantum well boxes which produce the quantum size effect, it is necessary to develop quite a new technique of forming quantum well boxes which may supersede the present electron beam lithography.